This study investigated a decade of candidates' performances in NECO-SSCE mathematics in NIGERIA. A total of 9266459 valid results were collated for the study and analyzed for zones in the country. Already validated results of NECO for 2000 to 2009 were used for the study. Three research questions guided the conduct of the study. Results showed that the highest number of valid results was recorded in the South-West zone while the North-East zone recorded the least. The South-South zone has the highest percentage performance and ranked the 1st position while North-East has the lowest percentage performance and ranked the least position (6th). Based on this result, the study recommended among other things that more qualified mathematics teachers should be employed as a matter of urgency in the North-East, North-West and North-Central zones to increase the workforce aimed at improving the teaching/learning of mathematics in these zones with a corresponding improved candidates performance in public examinations; Mathematics teachers in the South-South, South-West and South-East zones need to be commended and encouraged to put in more effort to sustain and improve on the present performance level.